Moreover, we noticed that DOX (targeting topoisomerase II), one of the first‐line chemotherapeutic drugs, synergistically suppressed osteosarcoma growth with pan‐HDAC (encoded by HDACs) inhibitor PXD101, ALK inhibitor LDK378, PRKCA (encoded by PRKCA) inhibitor Midostaurin, and NTRK1 (encoded by NTRK1) inhibitor Entrectinib (Figure 4E and Table S13). Here, HDAC9 is linked to osteosarcoma.